I. Field of the Invention
The present invention relates to data coding and decoding. More particularly, the present invention relates to a novel and improved method and apparatus for encoding data in orthogonal convolutional code form and the decoding of corresponding encoded data.
II. Description of the Related Art
The coding of digital message data is known to increase the reliability in communication of the data. Errors occuring in transmission of the data are much more likely to be detected should the data be coded. Coding of the data can provide an indication of the occurrence of errors in transmission and the correction of occuring errors.
Various coding techniques are used for preparing digital data for transmission. Examples of coding schemes include block codes and convolutional codes. In convolutional codes, parity-check information is distributed over a span of message symbols, called the constraint span of the code. Accordingly, long streams of message bits can be encoded continuously with out having to group the bits into blocks as is for block codes. Convolutional codes thus provide a unique scheme by which message bits may be simply and rapidly coded.
Implementations of convolutional coders and decoders are well known in the art. A basic implementation of a convolutional encoder is exemplified and described with reference to FIG. 1. Various implementations of decoders are well known and need not be discussed herein.
Orthogonal convolutional encoders are well known methods of generating codes with a large bandwidth expansion. The constraint length of the orthogonal code is, however, limited to the logarithm to the base 2 of the bandwidth expansion. This limits the power of the code in detecting and correcting errors.
It is therefore, an object of the present invention to provide a novel and improved convolutional encoder which is capable of providing a longer code constraint length for a given bandwidth expansion than conventional orthogonal convolutional encoders.
It is another object of the present invention to provide a novel and improved method of generating convolutional codes of large bandwidth expansion and long code constraint length.
It is yet another object of the present invention to provide a novel and improved method and apparatus for decoding super-orthogonal codes generated in accordance to the present invention.